Research has been carried out into two aspects of the cerebral circulation: (1) Its neurogenic control and (2) The basis of cerebral vasospasm. The response of cerebral blood vessels to electrical stimulation of intramural nerves has been studied in vitro. Their contractions appear to be mediated by adrenergic mechanisms involving in particular the alpha-adrenergic receptor, which is distinctive in these vessels in comparison to others. There is evidence of a non-adrenergic component to contraction. The transmission process in these vessels is particularly sensitive to modulation by autocoids. An in vitro model of cerebral vasospasm is under study. Discrete areas of constriction of the basilar artery are observed after its removal. These areas are associated with tares of internal elastic lamina. Their frequency is increased if the animal is made hypertensive prior to death. The role of tissue injury is under study.